The Leper of St. Giles: The Fifth Chronicle of Brother Cadfael

(From the back cover) Lovely, young, and well-dowried, Iveta de Massard is betrothed to the cruel and greedy Huon de Domville, a man well on in years. Gladly would she give her heart to young Joscelin, a noble squire who would adore her were she wealthy or not.
But before Joscelin can save his beloved from this odious marriage, Huon de Domville is found murdered. And Joscelin is forced to hide in a leper sanctuary, so
certain are his foes that he is the guilty one. Brave and true, amateur detective Brother Cadfael is not so certain. With care and more than a little courage, he sets about solving this marvelous mystery.